Re: [tip:x86/doc] x86/doc: mini-howto for using earlyprintk=dbgp

From: Daniel Walker
Date: Thu Mar 05 2009 - 17:40:37 EST


On Thu, 2009-03-05 at 11:22 -0800, Yinghai Lu wrote:

>
> thanks for checking it.
>
> can you submit patch to Ingo according to tip/master?


Hows this?

--

Fix up some typos, and make the requirements section slightly cleaner.

Signed-Off-By: Daniel Walker dwalker@xxxxxxxxxx

diff --git a/Documentation/x86/earlyprintk.txt b/Documentation/x86/earlyprintk.txt
index 607b1a0..5b51aef 100644
--- a/Documentation/x86/earlyprintk.txt
+++ b/Documentation/x86/earlyprintk.txt
@@ -9,7 +9,9 @@ and two USB cables, connected like this:

1. There are three specific hardware requirements:

- a.) Host/target system needs to have USB debug port capability.
+ a.) You will need two USB ports. One on the client/console system and one one the target system.
+
+ b.) The client/console and target USB ports must have the debug port capability.

You can check this capability by looking at a 'Debug port' bit in
the lspci -vvv output:
@@ -35,15 +37,13 @@ and two USB cables, connected like this:
( If your system does not list a debug port capability then you probably
wont be able to use the USB debug key. )

- b.) You also need a Netchip USB debug cable/key:
+ c.) You also need a Netchip USB debug cable/key:

http://www.plxtech.com/products/NET2000/NET20DC/default.asp

This is a small blue plastic connector with two USB connections,
it draws power from its USB connections.

- c.) Thirdly, you need a second client/console system with a regular USB port.
-
2. Software requirements:

a.) On the host/target system:
@@ -54,7 +54,7 @@ and two USB cables, connected like this:

And you need to add the boot command line: "earlyprintk=dbgp".
(If you are using Grub, append it to the 'kernel' line in
- /etc/grub.conf)
+ grub.conf (i.e. /boot/grub/grub.conf) )

NOTE: normally earlyprintk console gets turned off once the
regular console is alive - use "earlyprintk=dbgp,keep" to keep
@@ -72,7 +72,7 @@ and two USB cables, connected like this:

Now this channel of kernel messages is ready to be used: start
your favorite terminal emulator (minicom, etc.) and set
- it up to use /dev/ttyUSB0 - or use a raw 'cat /dev/ttyUSBx' to
+ it up to use /dev/ttyUSBx - or use a raw 'cat /dev/ttyUSBx' to
see the raw output.

c.) On Nvidia Southbridge based systems: the kernel will try to probe
@@ -92,7 +92,7 @@ and two USB cables, connected like this:

On the client/console system do:

- cat /dev/ttyUSB0
+ cat /dev/ttyUSBx

And you should see the help line above displayed shortly after you've
provoked it on the host system.


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